Silicone rubber cured products are used as rolls and other constituent members used in wet electrophotographic devices. The silicone rubber compositions used need to exhibit superior physical strength and suitable electrical conductivity.
Conventionally, room temperature-curable silicone rubber compositions are known as being suitable for use as sealants, but their use is limited due to problems pertaining to tensile strength, solvent resistance, and the like. In order to overcome such problems, the use of fluorosilicone rubber has been suggested.
For example, Japanese Unexamined Patent Application Publication No. H02-43264 describes a composition comprising a fluorosilicone polymer and a reinforcing silica for the purpose of providing a sealant with improved tensile strength. Japanese Unexamined Patent Application Publication No. H06-262621 and Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-505134 describe compositions comprising a fluorosilicone capped with silanols for the purpose of improving the solvent resistance and the like of a sealant. However, such compositions do not have electrical conductivity and, thus, lack characteristics that make them useful as anything other than compositions for use as sealants.
In contrast, using fluorosilicone rubber as a member used in a wet electrophotographic device has been suggested. For example, Japanese Unexamined Patent Application Publication Nos. H11-167295 and H07-295403 describe using electrically conductive fluorosilicone rubber as a surface layer on a metal drum of a wet photographic device. However, specific formulations of these fluorosilicone rubbers are not sufficiently recited and the electrical conductivity, and post-cure physical strength, surface smoothness, and other characteristics did not satisfy all of the required performance criteria.
Moreover, Japanese Unexamined Patent Application Publication No. 2004-221071 describes a carbonaceous material for an electrically conductive composition comprising vapor grown carbon fiber having a specific structure and graphite particles and/or amorphous carbon particles, for the purpose of improving electrical conductivity and preventing migration in an electrically conductive coating or electrically conductive adhesive. Furthermore, silicone is recited as the resin component thereof. While this composition has superior electrical conductivity, problems pertaining to physical strength are also exhibited such as post-cure tensile strength and the like.
Thus, conventional room temperature-curable silicone rubber compositions are deficient in that both sufficient electrical conductivity and superior physical strength cannot be obtained in cases when the compositions are used in applications having electrical conductivity. Additionally, in such cases, post-cure surface smoothness, solvent resistance, and adhesion have not been satisfactory.
In light of the problems described above, an object of the present invention is to provide a room temperature-curable electrically conductive fluorosilicone rubber composition by which a cured product having both superior post-cure physical strength and electrical conductivity can be obtained. Another object of the present invention is to provide a room temperature-curable electrically conductive fluorosilicone rubber composition having viscosity that enables superior handling, and superior post-cure surface smoothness, solvent resistance, and adhesion.